The subject matter disclosed herein relates to motor control systems, particularly motor control systems in cooling systems.
FIG. 1 illustrates a prior art example of a motor control system. The system includes a variable frequency drive (VFD) 102 connected to an alternating current (AC) power source 104. The VFD 102 includes a rectifier 106 connected to a direct current (DC) bus 108, an inverter 110 and a VFD controller 109. The inverter is connected to a chiller motor 112. A motor controller 114 is mechanically connected to a chiller compressor 116 and is communicatively connected to the AC power source 104 and the chiller motor 112 via the VFD controller 109 and the inverter 110.
In operation, the rectifier 106 receives AC power from the AC power source 104 and rectifies the AC power to DC power. The DC bus 108 includes a capacitor that stores a capacitive charge and outputs DC power to the inverter 110. The inverter converts the DC power to AC power and drives the chiller motor 112. The motor controller 114 receives AC power from the AC power source 104 and sends control signals to control the chiller motor 112.
If AC power is lost to the system, the charge stored in the capacitor continues to power the chiller motor however; the motor controller may not receive power and may shutdown.